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2.4 Anatomy & Physiology - Hair & Nails

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Cosmetology State Board Exam Exam

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1 Introduction to the Cosmetology State Board Exam

1.1 About the Cosmetology State Board Exam 1.2 NIC vs State-Specific Exams 1.3 Exam Content Breakdown 1.4 How to Register and What to Expect 1.5 How to Use This Study Guide

2 Chapter 2: Scientific Concepts (35% of NIC Exam)

2.1 Infection Control & Sanitation 2.2 Bacteriology 2.3 Anatomy & Physiology - Skin 2.4 Anatomy & Physiology - Hair & Nails 2.5 Chemistry for Cosmetology 2.6 Electricity & Safety

3 Hair Care and Services

3.1 Hair Analysis and Consultation 3.2 Shampooing and Conditioning 3.3 Haircutting Fundamentals 3.4 Hairstyling and Finishing 3.5 Chemical Texture Services 3.6 Hair Coloring

4 Skin Care & Esthetics

4.1 Skin Analysis & Consultation 4.2 Facial Treatments 4.3 Hair Removal 4.4 Makeup Application

5 Chapter 5: Nail Care

5.1 Nail Anatomy & Disorders 5.2 Manicure Services 5.3 Pedicure Services 5.4 Nail Enhancements 5.5 Nail Art & Finishing

6 Chapter 6: State Licensing Requirements

6.1 How State Licensing Works 6.2 Training-Hour Requirements Across States 6.3 Exam Components: Theory and Practical 6.4 Application, Background Checks & Fees 6.5 Reciprocity, Endorsement & License Transfer 6.6 Renewal and Continuing Education 6.7 Scope of Practice & License Types 6.8 State Sanitation Rules & Discipline 6.9 Multi-State Comparison & Relocation Guide

7 Chapter 7: New York Cosmetology Exam

7.1 About the New York Cosmetology Exam 7.2 New York State Laws & Regulations 7.3 NY Written Exam Content 7.4 NY Practical Exam 7.5 NY-Specific Practice Questions

8 Chapter 8: Florida Cosmetology Exam

8.1 About the Florida Cosmetology Exam 8.2 Florida State Laws & Regulations 8.3 Florida Salon Requirements 8.4 FL Theory Exam Content 8.5 FL Clinical Exam Content 8.6 FL-Specific Practice Questions

9 Chapter 9: Test Strategies

9.1 Test-Taking Strategies 9.2 Preparing for the Written Exam 9.3 Preparing for the Practical Exam 9.4 Exam Day Checklist 9.5 Comprehensive Practice Questions 9.6 Final Review Checklist

2.4 Anatomy & Physiology - Hair & Nails

Key Takeaways Explain This Topic AI

The hair shaft has three layers: cuticle (outer protective), cortex (strength and color), medulla (inner core).

Hair growth cycle has three phases: anagen (growth, 2-7 years), catagen (transition, 2-3 weeks), telogen (rest, 3-4 months).

The nail matrix is the origin of the nail plate and, if damaged, causes permanent nail deformity.

The lunula is the visible white crescent at the nail base - part of the matrix.

Normal hair shedding is 50-100 hairs per day from telogen phase follicles.

Last updated: January 2026

Understanding hair and nail structure, growth cycles, and disorders is fundamental knowledge for cosmetologists. This section covers the anatomy you need for the NIC exam.

  • Part 1: Hair Anatomy
  • Hair Structure Overview

Hair is composed primarily of keratin , the same protein found in skin and nails. Each hair consists of two main parts:

  • Hair Follicle : Living structure below the skin surface
  • Hair Shaft : Nonliving visible portion above the skin

Loading diagram... Structure of the Hair

The Hair Shaft - Three Layers

  • Layer Location Composition Function
  • Cuticle Outermost Overlapping scales (like roof shingles) Protection, determines shine and texture
  • Cortex Middle (90% of hair) Elongated cells, melanin, keratin Strength, elasticity, color
  • Medulla Innermost core Air spaces and cells Insulation (may be absent in fine hair)

The Cuticle:

  • Transparent, colorless layer
  • Scales point away from the scalp (root to tip)
  • Healthy cuticle = smooth, shiny hair
  • Damaged cuticle = dull, rough, tangled hair
  • Chemical services open and affect the cuticle

The Cortex:

  • Contains the majority of the hair's structure
  • Location of melanin (pigment)

Responsible for:

  • Hair color
  • Strength and elasticity
  • Texture (straight, wavy, curly)
  • Target of permanent color, perms, and relaxers

The Medulla:

  • Central core of the hair
  • May be continuous, fragmented, or absent
  • More common in coarse, thick hair
  • Often absent in fine, vellus hair
  • Function not fully understood
  • The Hair Follicle
  • Structure Description Function
  • Hair Bulb Club-shaped base of follicle Contains cells for growth
  • Dermal Papilla Cone-shaped elevation at bulb base Blood supply and nutrients
  • Arrector Pili Tiny muscle attached to follicle Creates "goosebumps"
  • Sebaceous Gland Oil gland connected to follicle Lubricates hair and skin
  • Hair Growth Cycle

Hair grows in a continuous cycle with three distinct phases:

Loading diagram... The Three Phases of Hair Growth

  • Phase 1: Anagen (Growth Phase)
  • Duration : 2-7 years (determines maximum hair length)
  • Percentage : 85% of scalp hair is in anagen
  • Activity : Active cell division at the hair bulb

Characteristics :

  • Hair grows approximately 0.5 inches per month
  • Longer anagen = longer potential hair length
  • Affected by genetics, age, health, and hormones
  • Phase 2: Catagen (Transition Phase)
  • Duration : 2-3 weeks
  • Percentage : 1-2% of scalp hair
  • Activity : Growth stops, follicle shrinks

Characteristics :

  • Hair detaches from dermal papilla
  • Follicle shrinks to about 1/6 of original length
  • Signals the end of active growth
  • Phase 3: Telogen (Resting Phase)
  • Duration : 3-4 months
  • Percentage : 10-14% of scalp hair
  • Activity : Follicle is dormant

Characteristics :

  • Hair remains in follicle but is not growing
  • New hair begins to form beneath
  • At end of telogen, old hair sheds
  • Exogen (Shedding)
  • Old hair is released from the follicle
  • Normal shedding: 50-100 hairs per day
  • New anagen hair pushes out old telogen hair
  • Excessive shedding may indicate disorder
  • Hair Disorders
  • Types of Alopecia (Hair Loss)
  • Condition Cause Characteristics Treatment
  • Androgenic Alopecia Genetics, hormones (DHT) Male/female pattern baldness Minoxidil, finasteride
  • Alopecia Areata Autoimmune Patchy, round bald spots May regrow spontaneously
  • Telogen Effluvium Stress, illness, childbirth Diffuse shedding Treat underlying cause
  • Traction Alopecia Tight hairstyles Hair loss at hairline/temples Change styling practices
  • Anagen Effluvium Chemotherapy Rapid, widespread loss Hair regrows after treatment
  • Scalp Disorders
  • Condition Description Action
  • Dandruff (Pityriasis) Flaky scalp, dry or oily Can perform service with medicated shampoo
  • Seborrheic Dermatitis Severe dandruff, oily scales Refer to dermatologist if severe
  • Psoriasis Thick silvery scales Can service if mild; refer if severe
  • Pediculosis (Head Lice) Parasitic infestation DO NOT perform service; refer to physician
  • Tinea Capitis Fungal ringworm DO NOT perform service; refer to physician
  • Hair Shaft Disorders
  • Disorder Description
  • Trichorrhexis Nodosa Weak points causing breakage
  • Trichoptilosis Split ends
  • Monilethrix Beaded hair shaft
  • Canities Gray/white hair (natural aging)
  • Ringed Hair Alternating light and dark bands
  • Part 2: Nail Anatomy

Loading diagram... Complete Nail Anatomy

Key Nail Structures

  • Structure Description Function
  • Nail Matrix Origin of nail (under proximal fold) Produces nail plate cells
  • Lunula Visible white half-moon Visible part of matrix
  • Nail Plate Visible, hardened nail Protection
  • Nail Bed Skin beneath nail plate Supplies nutrients
  • Free Edge Part extending past fingertip Functional edge
  • Hyponychium Skin under free edge Protects nail bed
  • Eponychium Living skin at nail base Protects matrix
  • Cuticle Dead tissue attached to plate Seals eponychium to plate
  • Lateral Nail Folds Skin on sides of nail Protection, guidance
  • The Nail Matrix - Critical Structure

The nail matrix is the most important structure:

  • Origin of all nail plate cells
  • Located beneath the proximal nail fold
  • The lunula is the visible portion of the matrix
  • If the matrix is damaged, the nail will be permanently deformed
  • Matrix cells produce keratin that hardens into nail plate
  • Nail Growth
  • Rate : Approximately 0.1mm per day (3mm per month)
  • Fingernails : Replace completely in 4-6 months
  • Toenails : Replace completely in 12-18 months
  • Factors affecting growth: age, health, nutrition, season
  • Nail Disorders and Diseases
  • Nail Disorders (Can Usually Service)
  • Disorder Description Cause
  • Leukonychia White spots Minor trauma to matrix
  • Onychorrhexis Brittle, splitting nails Age, chemicals, dryness
  • Beau's Lines Horizontal ridges Illness, stress, trauma
  • Hangnails Torn cuticle/skin Dryness, nail biting
  • Ridges Vertical lines Aging, normal variation
  • Eggshell Nails Thin, flexible nails Illness, malnutrition
  • Nail Diseases (DO NOT Service)
  • Disease Description Action
  • Onychomycosis Fungal infection; thick, discolored Refer to physician
  • Paronychia Infection around nail fold Refer to physician
  • Onychia Inflammation with pus Refer to physician
  • Pseudomonas (Greenies) Green/black bacterial infection Refer to physician
  • Onycholysis Nail separating from bed May indicate underlying condition
  • Tinea Pedis (Athlete's Foot) Fungal skin infection Refer if active
  • When to Refuse Nail Service

Never perform nail services on clients with:

  • Signs of infection (redness, swelling, pus, pain)
  • Fungal infections (discolored, thick, crumbly nails)
  • Open wounds or cuts around the nail
  • Visible bacterial infections (green/black discoloration)
  • Any condition that appears contagious